Steel for permanent magnets



Patented Jam-l8, 1938 UNITED STATES PATENT OFFICE No Drawing. Application November 13, 1933, Serial No. 697,874. In Japan May 1, 1933 8 Claims.

This invention relates to improvements in alloys for permanent magnets and more particularly to an alloy consisting mainly of nickel, titanium, and iron, and has for its object to provide a permanent magnet which has a very high coercive force and long durability.

Heretofore commonly used magnet steels such as tungsten steel, chrome steel and the like have comparatively small coercive force of only to '70 gausses and if such alloy steels are used as a permanent magnet they lack durability and are especially unsuitable for a magnet of smaller dimension-ratio, that is, having a small ratio of the length and diameter. Moreover, such alloy steels are greatly affected by temperature variations and mechanical shocks and show unstable magnetic properties.

This invention is to obviate the above mentioned defects and to provide an alloy which is well adapted for a permanent magnet of a smaller dimension-ratio, and possesses stable magnetic properties for temperature changes and mechanical shocks and has particularly high coercive force.

The alloy of this invention can be obtained by melting together nickel, titanium, and iron in the proportion of 3 to 50% nickel, 1 to 50% titanium, and the remainder iron. The preferred composition of the alloy may be of 10 to- 40% nickel, 8.1 to 40% titanium. and the remainder iron. The molten product may be cast in a suitable mold or sucked up into a tube of refractory material to give a desired shape. The cast products are preferably annealed at a suitable temperature such as 500 to 800 C. to give it stability.

As above described, though the alloy of this invention may be obtained by melting together iron, nickel, and titanium at a proper proportion, yet it is more convenient in practice to use iron or mild steel, nickel, and ierro-titanium.

As an example, an alloy of this invention containing about 24% nickel, about 18% titanium and the remainder iron and small amount of impurities is cast in a metallic mold and then heated to about 650 C. for two hours and then cooled down slowly. Then the alloy shows the magnetic properties of about 5300 gausses in the residual magnetic induction and about 300 gausses of coercive force.

The alloys of the present invention mayalso contain one or more auxiliary elements such as copper, aluminium and manganese in the proportion of less than 20% each for a further increase of the residual magnetic induction and the coercive force the preferable amount of these auxiliary elements is from 0.5% to 6% each.

Accordingly the alloy of this invention is well adapted for the material of permanent magnets in general and more especially of smaller dimension-ratio and it has very stable structure at a temperature below about 700 C. and its magnetic properties are not substantially affected by the change of temperatures and thus it is most suitable for the material of permanent magnets for fine instruments and also for heat resisting permanent magnets.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An alloy comprising about 24% nickel, about 18% titanium and the remainder iron and small impurities, characterized by a coercive force of about 300 gausses.

2. A permanent magnet formed of an alloy comprising as essential ingredients 3 to 50% nickel, 1 to 50% titanium and at least 20% of iron, characterized by a coercive force in the neighborhood of 250 gausses or more.

3. A permanent magnet formed of an alloy comprising 10.1 to 40% nickel, 8 1 to'40% titanio umand the remainder iron and small impurities, characterized by a coercive force in the neighborhood of 250 gausses or more.

4. A permanent magnet formed of an alloy comprising about 24% nickel, about 18% titanium and the remainder iron and small impurities.

5. For permanent magnets an alloy comprising about 24% nickel, about 18% titanium and the remainder iron and small impurities, characterized by a coercive force of about 300 gausses.

6. A permanent magnet formed of an alloy according to claim 2 wherein copper is included to the extent of not over 20%.

7. A permanent magnet formed of an alloy according to claim 2 wherein aluminium is included to the extent of not over 20%.

8. A permanent magnet formed of an alloy according to claim 2 wherein manganese is included to the exent of not over 20%.

KOTARO HONDA. 

